I am wondering about the prevalence of time-travel plots in Star Trek. For the purposes of this question I am excluding short loop, or deja vu, scenarios. This should be limited to actual travel with the possibility of altering the timeline. For example TOS had 5:

  • Tomorrow is Yesterday
  • City on the Edge of Forever
  • Assignment: Earth
  • All Our Yesterdays
  • Star Trek 4: The Voyage Home

Naked Time doesn't count since the time travel is just an afterthought, opening the door for it being used later. Nor does Star Trek: Generations since its time travel is a closed loop for the purposes of bringing Kirk forward.

  • I think this needs a more precise definition of "instance". For example, the DS9 2-parter with Gabriel Bell has one major act of time-travel, and then several minor ones by the people hunting down the people lost in the major one, all of which go to different historical eras and could conceivably have altered the timeline. Is that one instance or many?
    – Micah
    Commented Jun 8, 2013 at 2:54

3 Answers 3


TOS has (including Naked Now) only 5 (of 72), one doesn't meet the definition.

TAS has 1 of 22

Movies: ST IV, Generations, First Contact, and the Alternate Timeline ST. Note that neither Generations nor the Alternate Timeline actually meet the requirements. 2 of 12, then.

TNG's 12 listed include several that don't meet the Question's limited definitions. Time Squared is only 6 hours, but the time disconnect is vital to the plot. Cause and Effect is a temporal loop, as is We'll always have Paris. Tapestry might not actually be time travel, but merely a projection by Q; likewise for All Good Things. Timescape involves only a few minutes of actual time travel. THis leaves either 6 or 8, depending on if one believes Q was actually having Picard move through time, or just displaying information. Also, note that I count Time's Arrow Part I and Time's Arrow Part II as separate. So 6 or 8 of 178

DS9 has 11 episodes, including a two-episode story. Only one, The Sound of Her Voice, doesn't appear to meet the requirements, since the only thing travelling through time is signal. 10 of 176.

Voyager is 12 of 172, including a two-episode story. Parallax and Time and Again are short travel. Eye of the Needle is communication-only. Death Wish involves Q; it may or may not be actual temporal travel. Timeless involves only communications, and for once, only one way. So, 7-8 episodes meet the criteria.

Enterprise has 10, including two two-part ones. Future Tense involves multiple very short temporal jumps of a few minutes each, and so doesn't count. Thus, 9 of 98.

Series TT Eps (Eps that meet Criteria) of Total Episodes
TOS: 5 (4) of 78
TAS: 1 of 22
Mov: 4 (2) of 12
TNG: 12 (6 or 8) of 178
DS9: 11 (10) of 176
Voy: 12 (7 or 8) of 172
Ent: 10 (9) of 98


There is a very long list on Memory Alpha of known time travel episodes. It appears on average there are ten or eleven time travel episodes for every franchise, not counting movies.

  • Enterprise (10)
  • Next Generation (11)
  • Deep Space Nine (11)
  • Voyager (12)
  • That partially explains Enterprises problems, almost as many as the series that had many more seasons.
    – AthomSfere
    Commented Jun 8, 2013 at 21:13

"Naked time" technically counts as a time travel episode. They did go back in time 71.2 hours after using spock's new intermix formula to restart the engines in a short time.

  • Can you give us some more details about what happened?
    – Edlothiad
    Commented Aug 19, 2017 at 6:59

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